Many marine propulsion units, such as outboard drives and inboard-outboard drives, utilize a forward-neutral-reverse transmission along with a twin propeller. The typical twin propeller system includes a vertical drive shaft which is operably connected to the engine and is journaled for rotation in the lower gearcase. The lower end of the drive shaft carries a beveled pinion which drives a pair of coaxial bevel gears. Mounted for rotation within the central openings of the bevel gears is an inner propeller shaft, the outer end of which carries a first propeller, while an outer propeller shaft is journaled around the inner shaft and carries the second propeller, which is located forwardly of the first propeller.
Incorporated with the typical twin propeller propulsion system is a sliding clutch mechanism having forward, neutral and reverse positions. When the clutch is moved to the forward drive position, the clutch mechanism will act to operably connect the propeller shafts to the respective bevel gears to thereby rotate both propellers in the opposite directions and move the watercraft forwardly. Movement of the clutch mechanism to the reverse drive position in the typical system, will operably engage only the inner propeller shaft with one of the bevel gears, while disengaging the outer propeller shaft, to thereby drive the watercraft in a reverse direction.